The invention relates generally to shellfish processing and more particularly to apparatus and methods for removing the heads and shells from shrimp.
Originally introduced because of the high labor costs of peeling small shrimp by hand, shrimp-peeling machines are now widely used in the shrimp-processing industry. Roller-type peeling machines, in particular, dominate the bulk shrimp-peeling industry. U.S. Pat. No. 2,778,055, Jan. 22, 1957, and U.S. Pat. No. 2,537,355, Jan. 9, 1951, describe the basic structure and principles of operation of roller-type shrimp peelers, which detach heads and shells from shrimp. But the fluids and slime squeezed from the heads of the shrimp coat the peeling rollers, which degrades their grip on the shrimp and peeling quality.
Deheading shrimp by hydrodynamic force is known from U.S. Pat. No. 5,195,921, Mar. 23, 1993. In that patent, a shrimp-laden fluid is pumped through conduit that abruptly narrows. The abrupt decrease in the cross-section of the conduit causes the flow to accelerate through the narrow cross section according to the Venturi Effect. Hydrodynamic forces caused by the change in cross-section tend to detach heads from shrimp. Because of the high-speed water flow and rollerless operation, the removal of heads is not degraded by shrimp fluids. As shown in FIGS. 1A and 1B, cold-water shrimp 10, for example, have a long, thin sixth segment 12 that is easy to damage. The joint 14 between the third and fourth segments is also susceptible to damage. The abrupt change in the cross-section of the conduit can cause shrimp to break at these and other weak spots.
Thus, there is a need for a shrimp-processing system that can dehead and shell shrimp without damaging shrimp meats.